Many systems have been developed for protecting and physically supporting different soil elevations. A rockery, for instance, uses large size rocks which interlock and lean against an earth slope to protect the slope from slides due to weather erosion. Unfortunately, rockeries provide little or no structural support for the retained soil and are not self-supporting. They require reasonably stable native soil and are ineffective for supporting fine, sand-like soil or water.
In the past, different methods have been used to construct earth retaining walls. Many systems use large manufactured block-type units that interlock or key together and rely on dead weight to function.
McLean, (U.S. Pat. No. 250,235), discloses the use of a prefabricated interlocking rectangular glass block having a full length groove and full length rib stacked one upon the other to build a glass retaining wall to hold back see water.
Schmidt, (U.S. Pat. No. 2,313,363), describes a prefabricated retaining wall using blocks made from undisclosed material which are laid one on top of another in staggering superimposed rows so that each block has a longitudinal tongue on its bottom surface which overlaps the inside top edge of the lower block.
Meheen, et al., (U.S. Pat. No. 4,050,254), discloses a prefabricated module retaining wall using a plurality of pre-cast tie-back elements attached to curve panels. Each tie-back consists of a horizontal leg which is buried in the retained soil and exposed vertical legs. The curved panels attach to the vertical legs and act to retain the soil.
Sheehan, (U.S. Pat. No. 4,067,166), discloses the construction of a retaining wall using interlocking tongue and groove boxes having an elongated reinforced support bar buried in the soil.
In the related building construction art, Wolfe, (U.S. Pat. No. 2,160,773), discloses the use of interlocking concrete slabs having a plane outer side and a traversely curved inner side. The slabs have reinforcing wires with looped ends which extended through rabbeted ends on each slab. These ends are abutted and the loop ends are then placed around vertical steel bars which hold the slab in place.
Another group of earth supporting systems seen in the prior art use elements placed horizontally into the retained earth. These elements may be rigid or consist of a mat-like structure made of pencil strands which are laid horizontally and covered with compacted earth. Both the rigid members and the mats are structurally attached to a pre-cast concrete interlocking pattern of wall units to form the system. In order to construct this type of wall system, a large horizontal area, adjacent to the wall is required. Since such areas are not always available, these systems can not be used in many situations.
The basic structure of a concrete retaining wall includes a footing of varying size and a relatively narrow vertical concrete wall attached to it. Structural reinforcing the rods are placed in such a manner that, in combination, the wall and the footing operate as a single unit. Using this type of retaining wall, a structural engineer can predictably and safely design a retaining wall to combat the forces found in the specific field conditions.
None of the prior art, however, discloses retaining wall systems using pre-cast, reinforced concrete modules combined with cast-in-place structural elements as disclosed herein.